System and a method for locating a mobile terminal, in particular for rescuing in distress, and a device for alerting a corresponding mobile terminal

ABSTRACT

A system for locating a mobile terminal, in particular for rescuing a person in distress equipped with the said mobile terminal. The mobile terminal is of a type able to communicate via the base stations of at least one radio-communication system. The system comprises: at least a device for alerting the mobile terminal, transported by an aircraft and comprising a repeater connected to the first and second antennae, the said first antenna enabling the repeater to communicate with one of the base stations, the said second antenna enabling the repeater to create a specific, limited radio-communication coverage zone, located close to the aircraft, and to communicate with the mobile terminal, if the latter is located in the coverage zone, in such a way as to alert the mobile terminal and to force it to transmit at least a first message; means for locating the mobile terminal based on the said first message transmitted by the mobile terminal.

FIELD OF THE INVENTION

[0001] The field of the invention is that of systems for locatingpeople.

[0002] The invention applies in particular, but not exclusively, to thelocation of people in distress, with a view to rescuing them in anemergency situation.

[0003] More precisely, the invention relates to a system for locating amobile terminal, in particular for rescuing a person in distressequipped with the said mobile terminal.

BACKGROUND OF THE INVENTION

[0004] There are numerous situations in which it is necessary toprecisely locate such people. In particular, in order to increase thesafety of people in hazardous areas, there is a clearly expressed needfor a system enabling rescue teams to provide rapid assistance to peoplein distress, such as:

[0005] people trapped beneath snow following an avalanche;

[0006] people who are unconscious following an accident in themountains, for example a fall into a ravine, a crevasse, etc.;

[0007] survivors of a plane crash in an uninhabited area;

[0008] pleasure craft sailing close to coasts;

[0009] etc.

[0010] Until now, the solutions used are based on radiotransmitter/receiver type detection systems, which are manual systems,with a short range and used by a large number of people on the ground.Typically, a search and rescue team deployed to explore an avalanchezone comprises between twenty and fifty people using, in addition to theaforementioned manual systems, two or three metre long poles.

[0011] For example, for mountain rescue, the recognised systems are the“ARVAR 9000 Avalanche Beacon” (trademark) and the “RECCO” (trademark).

[0012] These recognised systems and methods have major drawbacks.

[0013] Firstly, because they have a short range, they do not provide anoverall view of a search area.

[0014] Equally, because of their short range (60 metres in theory), theycannot be effectively used on board helicopters.

[0015] Moreover, they require a relatively large investment by thosepeople who wish to protect themselves (for example, people in themountains who could be caught in an avalanche).

[0016] Furthermore, such an investment only enables the person to belocated by the given system, among a wide range of systems that areincompatible. It therefore appears difficult to require a person toinvest in different equipment for various location systems.

[0017] The wide range of recognised location systems, and theirincompatibility with each other, also poses a problem for theorganisations that are responsible (for example, in France localcouncils in ski areas), being forced to choose a location system withthe full knowledge that a low percentage of the population at risk islikely to benefit from it.

[0018] The invention has, in particular, the objective of abolishing orsignificantly reducing the various drawbacks of the current technology.

[0019] More precisely, one of the objectives of this invention is toprovide a system for locating people that covers a much largerpopulation than the current systems.

[0020] The invention also aims to provide a system that can locatesimply, whatever the terrain in which the person to be located may befound.

[0021] Another objective of the invention is to provide a system that,in most cases, does not require any investment by the people who wish toprotect themselves.

[0022] An additional objective of the invention is to provide a systemthat enables the number of people in a search and rescue team to bereduced.

SUMMARY OF THE INVENTION

[0023] These different objectives, as well as others that willsubsequently appear, are achieved according to the invention by using asystem for locating a mobile terminal, in particular for rescuing aperson in distress equipped with the said mobile terminal, the mobileterminal being of a type able to communicate via base stations of atleast one radio-communication system. The said location systemcomprises:

[0024] at least a device for alerting the mobile terminal, transportedby an aircraft and comprising a repeater connected to the first andsecond antennae, the said first antenna enabling the repeater tocommunicate with one of the base stations, the said second antennaenabling the repeater to create a specific, limited radio-communicationcoverage zone, located close to the aircraft, and to communicate withthe mobile terminal, if the latter is located in the coverage zone, insuch a way as to alert the mobile terminal and to force it to transmitat least a first message;

[0025] means for locating the mobile terminal based on, at the least, afirst message transmitted by the mobile terminal.

[0026] The general principle of the invention is therefore based on acombination of the following characteristics:

[0027] to locate a person, it is necessary to locate a mobile terminalthat the person is carrying;

[0028] a device for alerting the mobile terminal is taken onto anaircraft (preferably a helicopter), this device comprising a repeaterworking with the first and second antennae;

[0029] the mobile terminal is located using a message or messages(typically an access message) that it transmits after having beenalerted.

[0030] This invention therefore benefits from the fact that mobileterminals (mainly mobile phones) are now widespread. According to recentofficial sources, 450 million mobile phones are widely used around theworld, and in France 40% of the population already has one.

[0031] In particular, the latest evaluation carried out by the Pelotondes Guides de haute Montagne (PGHM) [Mountain Rescue Service] inChamonix showed that 50% of the calls that it receives are made bymobile phones able to be located by the radio-communication network(GSM). In the French, Swiss and Italian Alps, approximately 90% ofpeople carry a mobile phone, for safety and for personal use. The smallsize and low weight of this communication device means that it can beused during leisure activities in mountains that are covered by thenetwork.

[0032] In this manner, the use of a mobile phone in a rescue contextguarantees maximum coverage of the population in the area (for examplein the mountains).

[0033] Moreover, by taking the alerting device onto an aircraft(preferably a helicopter), people in distress can be rapidly located.

[0034] The repeater easily and effectively allows the coverage zone forbase stations to be enlarged, by creating a specific and limitedcoverage zone, located close to the aircraft. The use of a repeateroffers a real advantage because the latter is easy to set up and toconfigure. Furthermore, a repeater is compact and cheap, in particularwhen compared to a base station simulator. Its low power consumptionenables it to be used on board a helicopter.

[0035] The system set forth by this invention also enables the use ofsearch teams to be limited, as well to reduce the number of people insuch teams, who are charged with the final location and release ofpeople (trapped under the snow, for example).

[0036] The said aircraft should preferably be a helicopter.

[0037] Helicopters offer numerous advantages (speed, manoeuvrability,access to practically any location, etc.). It is nevertheless clear thatthis invention can be used with other types of aircraft.

[0038] The said mobile terminal should preferably belong to the groupcomprising mobile phones, personal digital assistants, etc. This list isnot exhaustive.

[0039] For the best performance the said first antenna should be ahelical antenna or equivalent.

[0040] For the best performance the second antenna should be a highlydirectional antenna, whose degree of directivity should be between 6°and 8°.

[0041] An advantageous characteristic is that the said repeater isfitted with an anti-larsen device.

[0042] The principle of an anti-larsen device shall be brieflyexplained. This repeater receives a remote, low energy leveltransmission on a first antenna (A), amplifies it, and re-transmits itunchanged via a second antenna (B). If the first and second antennae (Aand B) are not well insulated from each other, the first antenna (A)will receive the transmission from the second antenna (B) and the systemwill fall over: nothing more can happen. The anti-larsen device detectsthat the first antenna (A) is receiving the transmission from the secondantenna (B) and a special circuit “deletes” the transmission from thesecond antenna (B) received by the first antenna (A).

[0043] In an advantageous version, the said repeater is a repeater withfrequency translation.

[0044] The principle of a repeater with frequency translation will bebriefly explained. To prevent a “fatal” crash by the repeater, therepeater with frequency translation receives a transmission on a firstfrequency F_(A) via a first antenna (A) and changes the frequency toretransmit it from a second antenna (B) on a second frequency F_(B),which is different from the first frequency F_(A). As a consequencethere is no need for a larsen device.

[0045] In an initial specific embodiment of the invention, the saidmeans for locating the mobile terminal is of a type using a techniquebased on the directivity of the said second antenna.

[0046] In a second specific embodiment of the invention, the said meansfor locating the mobile terminal is of a type using a technique based ongoniometry.

[0047] These initial and second specific embodiments of the inventioncan be combined.

[0048] Most preferably, the system set forth in this invention alsocomprises:

[0049] means for analysing at least one radio-communication interface,in such a way as to retrieve at least the said first message transmittedby the mobile terminal;

[0050] means for processing at least a first message transmitted by themobile terminal and retrieved by the means for analysing the interface,in such a way as to recover an ID for the mobile terminal;

[0051] means for sending at least a second message to the mobileterminal whose ID has been recovered, to force it to transmit at least athird message acknowledging receipt and/or answering;

[0052] in such a way that the said location means can locate the mobileterminal from the said first message and from the said third messagetransmitted by the mobile terminal.

[0053] In this way, the mobile terminal is forced to transmit severalmessages, which makes it easier to locate, in particular by applying agoniometry technique to the messages received, coming from the mobileterminal.

[0054] Preferably, the said radio-communication interface should belongto the group comprising:

[0055] the (Um) interface between the repeater and the mobile terminal;

[0056] the interfaces (A-b) between the base stations (BTS) and the basestation controllers (BSC) to which the base stations are connected.

[0057] In an advantageous version of the system set forth by theinvention, in the said device for alerting the mobile terminal, therepeater is replaced by a “mini radio-communication network”.

[0058] The invention also relates to a device for alerting a mobileterminal with a view to locating it, in particular for rescuing a personin distress equipped with the said mobile terminal, the mobile terminalbeing of a type able to communicate via base stations of at least oneradio-communication system. The said device for alerting the mobileterminal is designed to be transported by an aircraft and comprises arepeater connected to a first and second antenna, the said first antennaenabling the repeater to communicate with one of the base stations, thesaid second antenna enabling the repeater to create a specific, limitedradio-communication coverage zone located close to the aircraft, and tocommunicate with the mobile terminal if it is located in the coveragezone, in such a way as to alert the mobile terminal and to force it totransmit at least a first message, in such a way that the locationequipment can locate the said mobile terminal on the basis of the saidfirst message transmitted by the mobile terminal.

[0059] The invention also relates to a method for locating a mobileterminal, in particular for rescuing a person in distress equipped withthe said mobile terminal, the mobile terminal being of a type able tocommunicate via base stations of at least one radio-communicationsystem. The said method comprising the following steps:

[0060] an aircraft transporting at least a device for alerting a mobileterminal is flown over a search area, the said alerting devicecomprising a repeater connected to a first and second antenna, the saidfirst antenna enabling the repeater to communicate with one of the basestations, the said second antenna enabling the repeater to create aspecific, limited radio-communication coverage zone located close to theaircraft;

[0061] the said alerting device transmits a predetermined signal, insuch a way as to alert the mobile terminal if it is located in thecoverage zone, forcing it to transmit at least a first message;

[0062] the mobile terminal is located using the said first message thatit has transmitted.

BRIEF DESCRIPTION OF THE DRAWING

[0063] Other characteristics and advantages of the invention will becomeapparent on reading the following description, according to a preferredembodiment of the invention, given as a purely indicative andnon-limitative example, and the appended drawings, in which:

[0064] the single FIGURE shows a specific embodiment of a system forlocating a mobile terminal set forth in the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] The invention therefore relates to a system and method forlocating a mobile terminal, in particular for rescuing a person indistress equipped with this mobile terminal.

[0066] In a conventional fashion, the mobile terminal is of a type ableto communicate via the base stations (BTS) of a radio-communicationsystem.

[0067] The invention applies to all types of radio-communicationsystems, in particular, but not exclusively, using the GSM (GlobalSystem for Mobile Communications), DCS 1800 (Digital Cellular System1800 MHz), PCS 1900 (Personal Communication System), DECT (DigitalEuropean Cordless Telecommunications), UMTS (Universal MobileTelecommunications) standards etc.

[0068] Throughout the description, it is presumed that the mobileterminal is a mobile phone 5. It is nevertheless clear that theinvention is not limited to this specific type of mobile terminal.

[0069] In the embodiment illustrated in the single FIGURE, the locationsystem set forth in the invention comprises:

[0070] a device for alerting a mobile phone, transported by a helicopter1 and comprising a repeater 2 connected to the first and second antenna3 & 4;

[0071] equipment 7 for locating a mobile phone from one or more messagestransmitted by the mobile phone.

[0072] The first antenna 3 enables the repeater 2 to communicate (asillustrated by the arrow marked 8) with one of the base stations (BTS)6. The first antenna 3 (or BTS-repeater antenna) should preferably be ahelical or equivalent antenna.

[0073] The second antenna 4 enables the repeater 2 to create a specific,limited radio-communication coverage zone located close to thehelicopter, and to communicate (as illustrated by the arrow marked 9)with the mobile phone if it is located in the coverage zone. In thisway, the repeater 2 will alert the mobile phone (in particular bytransmitting a BCCH carrier in the case of a GSM system) and force it totransmit at least a first message (an access request transmitted on theRACH channel in the case of a GSM system).

[0074] The second antenna 4 (or repeater-mobile phone antenna) shouldpreferably be a highly directional antenna, for example a vertical panelantenna mounted horizontally.

[0075] In other words, the repeater 2 performs the following functions:

[0076] thanks to the second antenna 4, it repeats, with or withoutfrequency translation, signals (in particular the BCCH carrier in thecase of a GSM system) coming from a base station, which it has receivedthanks to the first antenna 3. It is in this way that the repeater 2creates a specific, limited radio-communication zone located close tothe helicopter 1;

[0077] thanks to the first antenna 3, it repeats to the aforementionedbase station, with or without frequency translation, signals (inparticular access requests received on the RACH channel in the case of aGSM system) coming from a mobile phone and which it has received thanksto the second antenna 4.

[0078] Preferably, a repeater with an anti-larsen device should be used(for example the “MIKOM” model (trademark)) or a repeater with frequencytranslation.

[0079] It should be noted that the repeater 2 can be carried by ahelicopter, because the helicopter 1 is limited to 400 W of power and arepeater consumes on average 100 W for a gain of 10 W.

[0080] For example, a broadband repeater (ETSA) with the followingcharacteristics should be used:

[0081] average gain and power output;

[0082] low cost;

[0083] a gain of 40-60 dB;

[0084] power of 10 mW;

[0085] noise of approximately 8 dB;

[0086] weight of approximately 10 kg.

[0087] In the case of a radio-communication system using the GSM and DCS1800 standards, a broad band 900 MHz and 1800 MHz repeater can be usedto process all of the GSM and DCS bands.

[0088] The repeater can also be set to one particular channel, with orwithout frequency translation.

[0089] The equipment 7 for locating a mobile phone can be of a typeusing a technique based on the directivity of the second antenna 4and/or a technique based on goniometry.

[0090] A first technique based on the directivity of the second antenna4 shall now be presented. To focus the RF energy on the useful zones,the operators have developed highly directional antennae on a verticalplane, with between 6° and 8° of opening at 3 dB. These antennae arerelatively bulky “panels” (2.5 metres long for 900 MHz and 1.3 metreslong for 1800 MHz). The technique proposed for this invention consistsof using these antennae by mounting them horizontally and notvertically, in this case the RF energy is concentrated on a veryrestricted sector, tracing a narrow line on the ground. By passing overthe area twice, it is easy to cross these lines and to locate the searcharea with a high degree of precision.

[0091] In a second embodiment, based on goniometry, the antennae arearranged in a ring (for example, eight antennae positioned equidistantlyand therefore spread around the circumference of a circle). A specialreceiver captures the energy received by each of the antennae with thetime of reception of each binary element. The displacement measured inthis way reveals the direction of the transmission that has beenreceived. As with the first technique outlined above, at least twoover-flights are needed to pinpoint the precise search area.

[0092] A version of the location system set forth by the invention ispresented, in which the system also comprises:

[0093] equipment for analysing at least one radio-communicationinterface, in such a way as to capture the first message mentioned above(an access request transmitted on the RACH channel in the case of a GSMsystem) transmitted by the mobile phone;

[0094] equipment for processing this first message transmitted by themobile phone and captured by the interface analysis tools, in such a wayas to recover a mobile phone ID (for example, its IMSI number);

[0095] equipment for sending one or more second messages preferably in aburst (for example, short “SMS” messages in the case of a GSM system) tothe mobile phone whose ID has been recovered, to force it to transmitone or more third messages acknowledging receipt and/or answering(“Acknowledge Message” in GSM terminology).

[0096] So, in this version, the location equipment 7 described above canlocate the mobile phone not only by using the first message but also byusing the third messages transmitted by the mobile phone.

[0097] The aforementioned analysis equipment may comprise one or moreprotocol analysers, used to analyse the Um interface, between therepeater 2 and the mobile terminal 5, and/or the A-b interfaces, betweenthe base stations (BTS) 6 and the base station controllers (BSC) towhich they are connected.

[0098] Operation of this version of the location system set forth by theinvention can be summarised as follows:

[0099] the alerting device in the helicopter alerts the mobile phone 5,by transmitting strongly over a limited area (second highly directionalantenna 4). In a general manner, the system set forth by the inventiontherefore enables specific, limited coverage to be created close to thehelicopter, over the site of the accident. The following two cases canbe distinguished: either there is no GSM coverage (or other type ofcoverage) at the site of the accident and in this case it is created, orthere is already GSM coverage (or other type of coverage) and in thiscase the mobile phone is forced to relocate by frequency translation;

[0100] the mobile phone 5 attempts to register by issuing an accessrequest (first message) via the RACH channel;

[0101] an ID is recovered from the mobile phone by capture (on the A-bor Um interface) and the access request is processed. This step can beimplemented by one or more operators, who are asked to identify the basestation(s) covering the site of the accident (for example a mountainarea) and to observe the interfaces (for example A-b) by using protocolanalysers (samplers);

[0102] bursts of short messages (SMS) are sent (second messages) toforce the mobile phone to transmit messages acknowledging receipt (thirdmessages). These short messages can be initiated by any recognisedequipment (via the internet, modified mobile phones, the GPRS service,etc.);

[0103] the phone is located (using a technique based on the directivityof the second antenna and/or on goniometry) after the mobile phone hassent several (first and third) messages.

[0104] In another version of the location system set forth by theinvention, the repeater 2 is replaced by a “mini radio-communicationnetwork”, for example using the “INTERWAVE” model (trademark).

[0105] It should be noted that a “mini radio-communication network” is adevice that integrates, within a restricted range of functions, thevarious components of a radio-communication infrastructure. For example,in the case of GSM, it integrates the functions of the followingcomponents:

[0106] HLR (“Home Location Register”, nominal location recording),

[0107] VLR (“Visitor Location Register”, visitor location recording),

[0108] MSC (“Mobile Services Switching Center”, mobile serviceswitching),

[0109] BSC (“Base Station Controller”, base station controlling)

[0110] BTS (“Base Transceiver Station”, base station),

[0111] In this manner, the “rack” for the mini network is a PLMN initself. It can operate with mobiles that are “roaming” and in particularwith their attempts to register, which will be used for location.

[0112] Although the present invention has been described with referenceto preferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed is:
 1. A system for locating a mobile terminal, inparticular for rescuing a person in distress equipped with the saidmobile terminal, the mobile terminal being of a type able to communicatevia base stations of at least one radio-communication system, the saidlocation system being characterised in that it comprises: at least adevice for alerting the mobile terminal, transported by an aircraft andcomprising a repeater connected to the first and second antennae, thesaid first antenna enabling the repeater to communicate with one of thebase stations, the said second antenna enabling the repeater to create aspecific, limited radio-communication coverage zone, located close tothe aircraft, and to communicate with the mobile terminal, if the latteris located in the coverage zone, in such a way as to alert the mobileterminal and to force it to transmit at least a first message; means forlocating the mobile terminal based on the said at least one firstmessage transmitted by the mobile terminal.
 2. A system according toclaim 1, characterised in that the said aircraft is a helicopter.
 3. Asystem according to claim 1, characterised in that the said mobileterminal belongs to a group comprising: mobile phones; personal digitalassistants.
 4. A system according to claim 1, characterised in that thesaid first antenna is a helical antenna or equivalent.
 5. A systemaccording to claim 1, characterised in that the said second antenna is ahighly directional antenna, whose degree of directivity is between 6°and 8°.
 6. A system according to claim 1, characterised in that the saidrepeater is a repeater fitted with an anti-larsen device.
 7. A systemaccording to claim 1, characterised in that the said repeater is arepeater with frequency translation.
 8. A system according to claim 1,characterised in that the said means for locating the mobile terminal isof a type using a technique based on the directivity of the said secondantenna.
 9. A system according to claim 1, characterised in that thesaid means for locating the mobile terminal is of a type using atechnique based on goniometry.
 10. A system according to claim 1,characterised in that it also comprises: means for analysing at leastone radio-communication interface, in such a way as to retrieve the saidfirst message transmitted by the mobile terminal; means for processingthe said first message transmitted by the mobile terminal and retrievedby the means for analysing the interface, in such a way as to recover anID from the mobile terminal; means for sending at least a second messageto the mobile terminal whose ID has been recovered, to force it totransmit at least a third message acknowledging receipt and/oranswering; in such a way that the said location means can locate themobile terminal from the said first message and from the said thirdmessage transmitted by the mobile terminal.
 11. A system according toclaim 10, characterised in that at least one said radio-communicationinterface belongs to the group comprising: the interface (Um) betweenthe repeater and the mobile terminal; the interfaces (A-b) between thebase stations (BTS) and the base station controllers (BSC) to which thebase stations are connected.
 12. A system according to claim 1,characterised in that in the said device for alerting the mobileterminal, the repeater is replaced by a “mini radio-communicationnetwork”.
 13. A device for alerting a mobile terminal with a view tolocating it, in particular for rescuing a person in distress equippedwith the said mobile terminal, the mobile terminal being of a type ableto communicate via base stations of at least one radio-communicationsystem, characterised in that the said device for alerting the mobileterminal is designed to be transported by an aircraft and comprises arepeater connected to a first and second antenna, the said first antennaenabling the repeater to communicate with one of the base stations, thesaid second antenna enabling the repeater to create a specific, limitedradio-communication coverage zone located close to the aircraft, and tocommunicate with the mobile terminal if it is located in the coveragezone, in such a way as to alert the mobile terminal and to force it totransmit at least a first message, in such a way that the locationequipment can locate the said mobile terminal using the said firstmessage transmitted by the mobile terminal.
 14. A method for locating amobile terminal, in particular for rescuing a person in distressequipped with the said mobile terminal, the mobile terminal being of atype able to communicate via base stations of at least oneradio-communication system, the said method being characterised in thatit comprises the following steps: an aircraft transporting at least adevice for alerting a mobile terminal is flown over the search area forthe mobile terminal, the said alerting device comprising a repeaterconnected to a first and second antenna, the said first antenna enablingthe repeater to communicate with one of the base stations, the saidsecond antenna enabling the repeater to create a specific, limitedradio-communication coverage zone located close to the aircraft; thesaid alerting device transmits a predetermined signal, in such a way asto alert the mobile terminal if it is located in the coverage zone,forcing it transmit at least a first message; the mobile terminal islocated using the said first message that it has transmitted.